Embodiments herein relate generally to image forming apparatuses (e.g., electrophotographic apparatuses and printers) and components for use therein. Some embodiments are drawn to improved delivery members for delivery (directly or indirectly) of a functional material to the surface of an imaging member (e.g., photoreceptor) in an image forming apparatus to reduce printing defects and extend the useful lifespan of the imaging member.
In electrophotographic printing, the charge retentive surface/imaging member, also known as a photoreceptor, is electrostatically charged by a charging unit (e.g., a bias charge member), and then exposed to a light pattern of an original image to selectively discharge the surface in accordance therewith. The resulting pattern of charged and discharged areas on the photoreceptor form an electrostatic charge pattern, known as a latent image, conforming to the original image. The latent image is developed by contacting it with toner or developer.
Long life photoreceptors can result in significant run-cost reductions. Improvement of long life photoreceptors has included the development of low wear protective overcoat layers. These protective overcoat layers can help dramatically reduce surface wear of imaging members. However, these layers can also introduce a host of unwanted issues caused by the poor interaction between a cleaning blade and the overcoat layer and increased lateral charge migration (LCM). The overcoats can be associated with extremely high initial torque and can result in print defects, poor cleaning, cleaning blade damage/failure and cleaning blade flip, and, in some cases, high initial torque can prevent the imaging member from turning and can cause a motor fault. High torque can induce mechanical stress and vibration in the cleaning blade, which can, in turn, result in deformation and acoustic squeaking of the blade. This can damage the blade surface enough to permit permanent toner contamination of the imaging member. The contamination is often characterized by lines of toner around the circumference of the imaging member that correlate with the damaged areas of the cleaning blade.
The performance of overcoated imaging members can be improved by applying a thin film of a functional material/lubricant (e.g., paraffin oil) using an extrinsic delivery system (such as a delivery member) to address both the LCM and friction/torque problems. The thin film of functional material can act to lubricate a cleaning blade. Examples of methods and apparatuses related to application of functional materials to address these problems are described in copending U.S. patent application Ser. No. 13/020,738 (U.S. Publication No. 20120201585); Ser. No. 13/192,215 (U.S. Publication No. 20130028636); Ser. No. 13/192,252 (U.S. Publication No. 20130028637); Ser. No. 13/279,981; and Ser. No. 13/437,472, the specifications of which are incorporated herein by reference in their entireties.
An issue related to certain delivery members having an outer polydimethylsiloxane (PDMS) matrix that deliver a paraffin oil to an imaging member is that the paraffin oil can passively diffuse from the PDMS matrix (even without being in contact with another object, such as a bias charge roll (BCR)). This passive diffusion of the paraffin oil out of the delivery member can cause the paraffin oil to pool against a BCR or imaging member when an image forming apparatus sits idle (e.g., as when turned off overnight). The passive leaking of paraffin oil from a delivery member is detrimental to an image forming apparatus (e.g., printer), because over-delivery of paraffin oil increases contamination and causes print defects (e.g., streaking or lack of toner development); and consumes/wastes the supply of paraffin oil.
It would be desirable to maximize the amount of functional material (such as paraffin oil) stored in a delivery member in order to maximize the delivery member's lifetime. However, passive diffusion of functional material is greater at higher loadings of functional material relative to the elastomer matrix in delivery members, such as in delivery members having high loadings of paraffin oil dispersed in a PDMS matrix. Thus, it would be desirable to reduce or minimize passive leaking of functional material from delivery members.